1. Technical Field of the Invention
The present invention relates generally to an angular position determining apparatus working to measure an angular position of a rotary member, and more particularly to such an angular position determining apparatus quipped with a plurality of magnetic sensors and a malfunction detector which is designed to determine an angular position of a rotary shaft accurately even if any of the magnetic sensors is malfunctioning.
2. Background Art
Typical angular position sensors working to measure an angular position of a rotary shaft are made up of a ring-shaped magnet with an N-pole and an S-pole arrayed in a circumferential direction thereof, a magnetic yoke disposed around the periphery of the magnet, and magnetic sensors. The magnetic yoke has formed therein radial grooves forming air gaps. The magnetic sensors are disposed within the air gaps and work to measure magnetic flux densities in the air gaps. The angular position sensor determines the angular position of the rotary shaft using outputs of the magnetic sensors. For instance, U.S. Pat. No. 5,528,139 to Oudet et al., issued Jun. 18, 1996 (corresponding to Japanese Patent No. 2842482) teaches such a type of angular position sensor.
The above type of angular position sensors do not have a malfunction detector and thus encounter a difficulty in determining the angular position of the rotary shaft if any of the magnetic sensors has failed.